MMP9 and idiopathic pulmonary fibrosis: Although genetic deletion of MMP9 in mice (and/or MMP2) had minimal effects in Ad-TGFβ-induced pulmonary fibrosis66, antibody-mediated MMP9 targeting demonstrated antifibrotic efficacy in a humanized immunodeficient model of IPF induced by IPF lung extracts, but only when fibrosis was promoted by “responder” IPF cells that had been shown to have reduced phosphorylated SMAD levels in response to a-MMP9 treatment in vitro63.